The present invention was initially developed with problems associated with the comminution of wood and timber materials in mind, and took into account problems associated with apparatus such as wood hoggers. However, such devices are now used for breaking down a range of other materials, rather than simply just wood. As an example of the types of materials that hoggers are now used to break down, are included materials such as: soft rocks, hard rocks, mild and thin scrap steels, various soft and mild scrap metals, masonry and cementitious demolitions materials, recycled roading such as asphalt and coarse chip roading surfaces, old tyres, green plant material, etc. As can be appreciated these materials cover a significant range of hardnesses, and other properties. Recycled roading may include hard rock material, while tyres include a significant proportion of steel from the belts and beads. These present a range of effects on the teeth of grinding assemblies.
While for simplicity reference may often be made to wood hoggers (regardless of the material they are required to break down), it should be appreciated that the present invention may be used in grinding discs, drums, and apparatus of all kinds and including, in particular, rock crushers and devices for breaking down scrap metal, as well as hoggers per se. It should be realised that descriptions given here in relation to wood hoggers are applicable to other types of comminuting and grinding down equipment.
A typical wood hogger comminuting wood is fed various types of wood and timber material, which are then broken into smaller size pieces. Typically grinding discs or drums are used in a variety of different types and designs of apparatus for comminuting wood material. Generally these discs and drums bear a plurality of teeth like protuberances which impact with the wooden material, or other materials being fed in.
However, in practice and even for wood, high wear is often seen. Some types of wood hoggers (which is a device typically for breaking down waste timber material into a low grade fuel called hog fuel) can suffer quite high wear due to continued contact with the material being processed, this being a consequence of their design, the materials being processed, and whether they are being overfilled during use. Accordingly most modern designs of grinding discs and drums have evolved to have replaceable teeth as opposed to teeth which are formed, welded, or otherwise cast into the main body of the drum or disc—which still exist in some designs.
A further problem associated with tooth wear is damage caused by impact with foreign material. Quite commonly steel and rocks may find their way into wood hogging apparatus (for instance) and can cause severe damage to teeth. The consequence of such impacts is sometimes more severe when a hard item is encountered when processing soft material, than when processing exclusively harder materials. However, in all situations the teeth will wear and may need to be replaced. For devices which are being used in a variety of roles (e.g. the typical wood hogger used for comminuting harder materials) there may also be a need to substitute teeth with those tipped with different materials. Regardless of the reason, teeth should be able to be completed as quickly as possible to avoid extended down periods for the apparatus while repairs, modifications, or maintenance are performed.
The problem with most prior art tooth designs are that while the tooth design is quite simple, the holder is relatively complex in design. The problem here is that they are more expensive to produce (though the replacement teeth may be relatively inexpensive) and often require discs and drums of specific design to be prepared so that the complex tooth holders can be fitted. This adds to the overall cost of constructing the original apparatus.
It is also common to find that the wear of teeth is predominately on one side, as most apparatus is designed to rotate in one particular direction only. Most current designs do not allow the orientation of the teeth or disc to be easily or quickly changed, and neither to they allow for reverse operation of the disc—which would often conflict with the operational design of the whole apparatus.
Accordingly there is a need in the industry for an alternative design which allows teeth, for use in grinding discs and drums, to be simply fitted, easily changed, and ideally also being able to be easily rotated to allow both sides of the tooth to be exposed to wear.
It is an object of the present invention to provide an improved replaceable tooth design which does not require a complex holder assembly for fitting to at least a grinding disc or port thereof.
It is an object of the present invention to address the problems of the prior art.
At the very least it is an object of the present invention to provide the public with a useful alternative.